hi guys
recent purchase of a cary rocket 88 amp. kt88 tubes now.
i'm seeing lots of online posts everywhere about swap to kt120 for a output power increase.
can anyone with tube history set me straight on this subject.
the only reason i ask is the kt88 in a cary rocket are said to produce about 40 watts. this doesn't seem like enough power.
thanks
gordie

Cary apparently runs this amp conservatively and rates it 20 watts in triode mode and 40 watts in UL mode. Power out is a function of power in to the tubes as well as operating configuration. Everything is somewhat of a trade-off between distortion, power out & tube life Simply replacing the output tubes with a beefier type will not increase power out.

__________________There cannot, and never will be, any progress in society, vis-a-vis racism, so long as the concept of celebrating Diversity -- in it's current, politically-correct, deliberate, punitively extractive form -- continues.

Cary apparently runs this amp conservatively and rates it 20 watts in triode mode and 40 watts in UL mode. Power out is a function of power in to the tubes as well as operating configuration. Everything is somewhat of a trade-off between distortion, power out & tube life Simply replacing the output tubes with a beefier type will not increase power out.

so i take that you suggest to just leave it alone right? the kt120 will be a waist of money?

why are a lot of people claiming better sonics and 15% more power output from a swap from kt88 to kt120.

so i take that you suggest to just leave it alone right? the kt120 will be a waist of money?

Yes.

Quote:

why are a lot of people claiming better sonics and 15% more power output from a swap from kt88 to kt120.

1) They spent a lot of money on the new tubes so they must perform better.
2) They replaced poor KT88s that need replacement anyway.
3) Their friends told them they sounded better.
4) They look much "cooler".
5) They somehow believe that bigger/newer really is better.
6) They didn't make true electronic measurements with calibrated instrumentation.
7) They were stoned.

Anyway, all seriousness aside , I have never used KT120s so I am unfamiliar with their actual preformance. If their operating point is sufficiently different along with their gain characteristics then KT88s, I suppose one might hear a difference in "apparent" gain. But I am speaking from basic design theory that dictates there is no free output power increase without increasing input power. What someone thinks they hear, or see, is extremely subjective.

Please, if you know of a post that has credible measured improvment data of KT120s replacing KT88s with nothing else done, I would like to read it.

__________________There cannot, and never will be, any progress in society, vis-a-vis racism, so long as the concept of celebrating Diversity -- in it's current, politically-correct, deliberate, punitively extractive form -- continues.

guys
cary state the rocket 88 has a power supply built into this for 200% duty cycle and stock kt88 bias is 45 to 50 ma and the kt120 are listed to need i think around 68ma.
i've seen on youtube a guy who tests the kt88 then the kt120 . kt 88 produced 38 watts @.9 thd
kt120 when biased right produced 60 watts @ .78 thd.
it is this vid that makes me want to try it.
but like you say if 40 watts is not enough thats another story.
do you mean leave this amp as it is and build something more powerfull?